Ink jet printing is a non-impact and non-contact printing method in which an electronic signal controls and directs droplets or a stream of ink that can be deposited on a wide variety of substrates. Ink jet printing is extremely versatile in terms of the variety of substrates that can be treated, as well as the print quality and the speed of operation that can be achieved. In addition, ink jet printing is digitally controllable. For these reasons, ink jet methodology has been widely adopted for industrial marking and labeling. In addition, ink jet methodology has also found widespread use in architectural and engineering design applications, medical imaging, office printing (of both text and graphics), geographical imaging systems (e.g., for seismic data analysis and mapping), signage, in display graphics (e.g., photographic reproduction, business and courtroom graphics, graphic arts), and the like. Finally, ink jet printing has now also been used to create an image on a variety of textile substrates. The use of ink-jet printing to create an image on textile fabrics has allowed for the rapid visualization of an aesthetic design on fabric without the use of expensive and often wasteful screen printing techniques. Such ink-jet printing methodology allows a designer or production facility to visualize a finished design in significantly less time than is usually necessary to burn a screen image of the design by typical screen printing methodology.
Both dyes and pigments have been used as colorants for such ink jet ink formulations. However, such materials do not always adhere well to substrates to which the ink is applied. For example, dyes may dissolve upon a substrate's contact with water. Thus images applied employing ink jet methodology may tend to run or smear upon repeated contact, or may be actually removed from the printed surface if exposed to substantial quantities of aqueous media (e.g., if an ink jet printed article is laundered). Moreover, images applied employing ink jet methodology may also tend to fade or washout upon prolonged exposure to visible, ultraviolet and/or infrared light. Furthermore, dyes applied to textile substrates may experience severe dye bleed upon application to the substrate. Finally, the color intensity of the image printed on a textile substrate using ink-jet methodology is often lacking in vibrancy.
The nature of textile substrates also poses specific problems when printing or imaging via ink jet print methods, which are not found with common ink jet substrates (e.g. paper or coated paper). For instance, the textile fibers can vary widely in composition, with each composition presenting a unique set of conditions for acceptable printing of the substrate. For example, cotton substrates may be very absorbent, such as in the case of aqueous-based inks. When ink is ejected from the ink channel of an ink jet printing device, it is rapidly absorbed into the fibers of the cotton substrate. Since these fibers are much larger than the fibers typically found in paper substrates, the color density or appearance of color brightness is significantly diminished due to the lack of retention of the colorant at the surface of the fibers. In addition, bleeding, mottle of the print pattern, and loss of image sharpness or clarity can often result from printing on the textile fabric itself.
Conversely, synthetic fibers such as polyester may be poorly wet by the aqueous inks and such inks may be only retained in the interstitial spaces between the fibers. This limited ink retention also causes the print-quality related problems outlined above.
Furthermore, the permanence of the printed image on textile fabrics is often achieved commercially by some post-printing curing process such as heating, steaming, or chemical fixation. These processes tend to be inefficient, requiring further washing and drying steps to remove unfixed colorant from the fabric. It is therefore desirable to enhance the permanence of the printed image on ink jet printable substrates, either in the presence or absence of a post-printing curing process step.
Polymeric materials are typically used commercially to modify the properties of both natural and synthetic textile fibers and substrates. These polymeric treatments may alter textile appearance or hand, reduce shrinking, reduce flammability, or alter other properties of the fiber or substrate. Treatments may even be employed to enhance the ease of printing and/or print performance when commercial printing processes, such as rotary screen printing, are employed. For instance, polyethylene oxide has been used to pretreat a starting cloth material so as to create an adequate textile substrate for ink-jet printing. As disclosed in U.S. Pat. No. 5,781,216 to Haruta et al., the use of polyethylene oxide treated textile substrates are described as being highly capable of providing images of great color depth with sufficient brightness and sharpness, but free of objectionable color bleed. While Haruta discloses such a polyethylene oxide pretreatment with a cationizing agent, to thereby enhance the coloring ability of images, Haruta requires such treatment to thereafter be cured by additional heating, washing and drying steps.
Use of cationic polymers as part of a latex saturant in a hydroentangled fibrous web is disclosed in PCT US 98 11712 to Harris et al., which was published as WO99/00541. As described in WO99/00541, latex saturation is typically followed by a drying step or other curing aids.
Use of imbibing solutions with sodium bicarbonate, sodium carbonate and urea are also known. Such imbibing solutions are typically used by textile mills in ink pastes along with other additives such as thickeners, and not in conjunction with coating treatments on the textile substrates themselves prior to being printed. The ink pastes are then rotary screen printed down onto the fabric substrates. However, an ink jet paste delivery system can not be used for ink jet printing because of the physical constraints of the ink jet printer technology. The salts in the pastes will corrode the ink jet printer heads. Use of ink pastes are also a wasteful process. Furthermore, even with the use of such pastes in a conventional screen printing process, the process experiences a large amount of dye wash off following printing.
Accordingly, there is still a need in the art for ink jet printable substrate coatings and treatment methods which provide for high optical density with a minimum amount of bleeding on the substrate during and after imaging from ink jet printers. There is also a need in the art for such ink jet printable substrate treatment methods which can be applied to textile fabric substrates. In this regard, there is still a need in the art for methods for treating fabrics for receiving ink-jet ink formulations, which methods allow for improved colorfastness and color intensity in a wide variety of textile substrates. Finally, there is still a need in the art for such substrates which are not dependent upon an ink curing step for construction.